and advice to stop hooking the ball please

My son is having real problems at the moment hooking the ball,   he put a collection of swings on youtube himself a while ago (see below) from a wedge to a driver and he's going to try and put another more recent one on shortly. 

hopefully the video will work below but not sure how to put into slow motion so may not really show much.

can anyone give a list of thngs he can work through to try and stop hooking - driver is the worst but he is now hooking his low irons as well

he knows the club is pointing right of target at the top but really struggles to stop this. 

http://www.youtube.com/user/msh2k9123#p/u/4/OtXKTXWkeM0

thanks in advance.

John, he is a  flexible young man with a very good swing indeed. Being across the line at the top is because he is just swinging too far, this will alter once he gets a little stronger. It is something I used to do myself when I was fit . skinny and lithe.

ok thank you for the comments.

off to the range tonight so will see how it goes.